Expression data for heat tolerant and susceptible cultivars of indica rice

Heat stress along with other abiotic stresses is one of the major factors affecting crop health and overall yield in a tropical country like India. Thus, there is an urgent need to understand the dynamics of heat responsiveness at the molecular as well as physiological level. Fortunately, India has a number of indigenous varieties that show tolerance to extremes in temperature during the scorching summer months. The cultivar Annapurna is a fast growing dwarf variety of rice that is heat tolerant while the most widely grown indica rice in South and Southeast Asia, IR64, is susceptible to high temperatures. These two cultivars present an excellent opportunity to study the differences in response to heat stress, and, thereby help in elucidating the genes involved in conferring tolerance to high temperature. The present study involves transcript profiling of the two cultivars, Annapurna (tolerant) and IR64 (susceptible) under both control and heat stressed conditions. Seven-day-old seedlings of Annapurna and IR64, grown hydroponically, were subjected to heat stress by giving them pre-treatment at 37 oC for 1 h followed by exposure to a higher temperature of 42 oC for 2 h at 40% relative humidity in light conditions. For control samples, seedlings were kept in RGM (root growth medium) for 3 h at 28±1oC. RNA extracted from each sample was hybridized on rice Affymetrix microarrays. Three biological replicates of each sample were used for microarray analysis. Overall, eighteen samples were analyzed representing control, 37 oC and 42 oC of heat stress for each cultivar (Annapurna and IR64).